(CNN) -- A gap in communication between the National Weather Service and the Army Corps of Engineers undercut forecasts of the deadly flood that struck middle Tennessee in 2010, the National Weather Service reported Wednesday.

The Corps of Engineers was forced to increase the flow of water from a dam on the Cumberland River amid record rainfalls over Nashville and the surrounding region on May 2, according to a newly released National Weather Service review of the disaster. But forecasters weren't told about the additional releases, and the Cumberland passed its predicted crest of 41.9 feet within two hours of their advisory, the report states.

"If they had been able to provide that data back to the Weather Service, we could have had a better chance of producing a more accurate and timely forecast for the Cumberland River," said Weather Service meteorologist Jane Hollingsworth, the report's author. "But again, because of the rapid evolution of the event, we could not create that communication exchange."

The Cumberland eventually crested at nearly 52 feet in downtown Nashville, nearly 12 feet over flood stage. The resulting flooding killed 11 people in the city and inflicted more than $2 billion in damages, with another 15 people killed in the surrounding region.

Both Hollingsworth and Jack Hayes, the Weather Service's director, emphasized that the communication breakdown occurred during an "unprecedented" situation, when two-day rainfall totals more than doubled their previous record. The Corps had to increase water flows at the Old Hickory Dam in Hendersonville "to protect the structural integrity of this dam," Hollingsworth told reporters.

In its own November assessment, the Corps of Engineers acknowledged that "misunderstandings" between its Nashville district office and the Weather Service threw off forecasts "to some degree." Lt. Col. Anthony Mitchell, the district commander, told CNN that the Weather Service's report was "pretty fair" and consistent with the Corps' own report.

"Obviously, our normal protocols in how we would communicate were taxed, and they were taxed to a degree that we recognize that we need to improve upon," Mitchell said. But, he added, "Our actions and the actions of those Corps employees that were out there on the spillway gates, making adjustments, saved those projects and saved lives as well."

The Corps is working on ways to share real-time data with forecasters and other agencies that need it, he said.

Hollingsworth said that while the Weather Service issued flood warnings, many residents of the affected areas said they could not relate those warnings to the impact on their neighborhoods. As a result, she said, "All perceived that they had no warning."

Hayes said the Weather Service, the Corps of Engineers and the U.S. Geological Survey have taken steps to improve communication and to learn more about each others' operations in the wake of the event. And he said the service has developed forecast maps that relate predicted crests to maps, allowing residents to see a clearer picture of how far floodwaters will reach.

"They need to know, when the river reaches 48 feet, what that will mean for their homes and businesses," Hollingsworth said.